Abstract
This work presents a method of needle shape reconstruction, which can serve as potential guidance technology for minimally invasive surgeries, such as epidural anesthesia. The suggested technology applies four optical fibers, which are glued along the Tuohy needle at an angle of 90 degrees from each other thus creating two pairs of opposite fibers. Optical fibers are used to achieve high resolution distributed strain sensing along the needle, which working principle is based on the Optical Backscattering Reflectometry (OBR). Since OBR is limited to a single-fiber measurement and the setup requires four sensing fibers, the multiplexing method has been suggested. The multiplexing approach is based on the spatial separation of four high-scattering nanoparticles doped fibers (used as sensing fibers) by the single-mode regions with a lower scattering level. As a result of such configuration, the strain sensed by each sensing point along the pairs of opposite fibers is used to reconstruct the inclination of the needle in two perpendicular directions. The approach has been tested in the needle calibration experiment when it has been manually bent to different directions and the setup allowed to accurately reconstruct the direction of the needle‘s inclination. The potential application of the setup for the minimally invasive therapies has been tested on the example of epidural anesthesia. The needle has been inserted into a medical phantom, which models human spinal anatomy, and the shape of the needle at each moment of insertion has been reconstructed.